OK, your security bolts, you can release these using a socket, use one that is slightly too small to slot over the edge and hammer it onto the fairly soft security head, use a socket handle and breaker bar. Your security nuts are trash anyway. Worked for me.
If the mechanic did not torque the crankshaft bolt (negligence) to the correct tollerance (and it is huge btw, when I did mine the first socket ruptured as I was doing the angle turn) it would give you those symptoms. I agree, it would be highly unlikely valves have not collided with pistons at some point in this mess. Once you solve the crankshaft mystery, a cylinder pressure test would be next (no need to pull the head if pressures are good) and any loss would be a head off and valve stem check.
Cooper 2009, R57.